Month: November 2018

The Teaching Company, LLC offers hundreds of video courses under the name “The Great Courses” on just about every subject imaginable, with more being added all the time.

Though offered for personal in-home viewing, these 30-minute lectures (or 45-minute in the case of Robert Greenberg’s engaging music courses) would make a wonderful centerpiece for a continuing education course.

As an instructor, what I would like to be able to do is show my class a Great Courses lecture, and then follow that with discussion and activities that reinforce and expand upon those concepts during the remainder of a 60-minute or 90-minute class.

Not unlike what a good teaching assistant does in a college recitation section after a lecture by the professor, The Great Courses lecture would provide instructional scaffolding for both instructor and student.

I believe The Teaching Company has a great opportunity here. Just by allowing an instructor to show a course to students (and charging a reasonable fee to do so), they would be opening up a new market for their products, and would no doubt bring in many new individual customers.

The Teaching Company could provide the courses “as is”, or could make available supplemental materials for the continuing education teacher and their students.

I even have a name for this new offering: Great Courses Launchpoint.

Currently, The Teaching Company doesn’t exactly encourage the use of their materials for face-to-face teaching:

My hope is that they will see the value of incorporating their video lectures into the classroom, and maybe Great Courses Launchpoint will roll out by the time I semi-retire in three or four years. One of the frustrations of getting older is that my “day job” is taking a greater share of my time and available energy than ever before. I love teaching, though, and semi-retirement will afford me the opportunity to begin teaching on a regular basis again. Looking forward to it!

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but since October 4, 1957 another “species” of sky vermin made their debut: artificial satellites. In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my ~¼° field of view.

I’ve put together a video montage and some individual videos of satellites I’ve recorded between March 10, 2018 and November 24, 2018. All of the events are shown below, with the boldface events being presented chronologically in the first video. Both the NORAD and International designations are given for each satellite. The range is the distance between observer and satellite at the time of observation.

You’ll notice that sometimes the satellite crosses the field as a moving “dash”. That’s because sometimes I used longer exposure times to record a fainter target star. A wind gust hit the telescope during the second event (3-25-2018). The field is oriented North up and East to the left. In this first video, you’ll notice that Sentinel 1B (the last event) has a unusual retrograde orbit (sun-synchronous) and is moving towards the NW.

In general, the slower the satellite is moving across the field, the higher is its orbit around the Earth. One must also consider how much of the satellite’s orbital motion is along your line of sight to the satellite.

In the following video clip, you’ll see an unidentified piece of space debris, a very faint “dash” (due to integration) moving NE across the field from lower right to upper left, recorded on May 5, 2018 UT.

Next, we see a Ariane rocket body used to hoist SMART-1 towards the Moon and the Insat 3E and eBird 1 towards their geostationary orbits. This recording was made on July 6, 2018 UT. The rocket body is traveling NE (mostly east). The light curve below the video suggests the possibility of some tumbling motion, but the satellite is faint and the photometry noisy.

Here is a no-longer-operational Japanese communications satellite named Yuri 2A, launched in 1984 and captured here on August 3, 2018 UT. It is traveling NE (mostly east) and shows a beautiful long-period large-amplitude light curve.

Finally, we see not one but two geostationary communication satellites, Galaxy 17 (first and fainter) and NIMIQ 6 moving east across the field (as my telescope tracks westward to follow the Earth’s rotation), captured here on October 21, 2018 UT. Galaxy 17 exhibits no discernible rotation, but NIMIQ 6 shows a low-amplitude long-period change in brightness.

If you thought light pollution is bad (and it is!), radio pollution for radio astronomers is much worse. Even years ago, terrestrial pollution of the radio spectrum tended to swamp faint celestial sources at many frequencies, and in 1958 the FCC established a 13,000 square mile rectangular region of West Virginia, Virginia, and Maryland as the National Radio Quiet Zone. Two facilities within this protected region—whose natural topography helps to screen out many terrestrial radio emissions—are the Sugar Grove Station and the Green Bank Observatory near Green Bank, West Virginia. The world’s largest fully-steerable radio telescope dish was built at Green Bank in 1956. Though the original 300-ft. dish collapsed in 1988 due to a structural failure, it was rebuilt in 2000 as the Robert C. Byrd Green Bank Telescope, a leading facility for radio astronomy.

The best place in the world to do radio astronomy is not on our world at all but instead on the far side of the Moon. Radio telescopes deployed on the lunar farside could “listen” to the universe with absolutely no interference from Earth. The solid body of the Moon (and its lack of an atmosphere) would completely block all radio signals and noise emanating from the Earth and Earth orbit. And some radio telescopes could be quickly and easily deployed (think long-wire antennas rather than radio dishes). Of course, the Moon itself will need to be designated as a radio quiet zone so that any lunar colonies, rovers, or satellites operate at frequencies and times that will not interfere with scientific work. Maybe infrared or optical lasers would be a better way to communicate?

How would data from a lunar farside radio observatory be transmitted back to Earth? One way would be to have a dedicated lunar satellite that receives data from the radio observatory while it is traveling over the lunar farside. It would then re-transmit that data to Earth while it is traveling over the Earth-facing nearside.

Another (probably more expensive) approach would be to have a series of radio relay towers spaced at intervals from the radio observatory around to the lunar nearside where a transmitter could send the data back to Earth.

A third choice would be to locate the radio observatory in a libration zone along the border between the lunar nearside and farside. At a libration zone radio observatory, data would be collected and stored until each time libration allows a direct line-of-sight to Earth.

The crater Daedalus, near the center of the lunar farside, has been suggested as the best location for a radio astronomy facility on the Moon (Pagana et al. 2006).

There is also a region above the farside lunar surface where radio emissions from Earth and Earth-orbiting satellites, would be blocked by the Moon, called the “Quiet Cone”, as illustrated in the diagram below.

The Earth-Moon L2 Lagrange point (EML2) is probably going to be within the lunar quiet cone. Because L2 is an unstable Lagrange point, a radio telescope in the quiet cone would need to be in a halo orbit about EML2, and a tight one at that to avoid “seeing” any radio emissions from the highest Earth-orbiting satellites.

As of this writing, there are 3,635 comets named SOHO, over 300 comets named LINEAR, some 179 comets named PANSTARRS, 82 comets named McNaught, 62 comets named NEAT, and so on.

Except for the comets discovered by Scottish-Australian astronomer Robert H. McNaught (1956-), all of the above comets were named after various semi-automated surveys.

SOHO = Solar and Heliospheric Observatory (spacecraft)

LINEAR = Lincoln Near-Earth Asteroid Research

Pan-STARRS = Panoramic Survey Telescope and Rapid Response System

NEAT = Near-Earth Asteroid Tracking

How do we distinguish between comets having the same name? Each has a separate comet designation. The first Comet LINEAR has a designation of P/1997 A2, and the most recent Comet LINEAR has a designation of C/2017 B3.

A comet designation starts with one of the following prefixes:

P/ – a periodic comet (orbital period < 200 years or confirmed observations at more than one perihelion passage)

C/ – non-periodic comet (orbital period ≥ 200 years and confirmed observations at only one perihelion passage)

X/ – comet for which no reliable orbit could be calculated (generally, historical comets)

D/ – a periodic comet that has disappeared, broken up, or been lost

A/ – an object that was mistakenly identified as a comet, but is actually a minor planet (asteroid, trans-Neptunian object, etc.)

I/ – an interstellar object that did not originate in our solar system

This is then followed by the year of discovery, a letter indicating the half-month of discovery, followed by the numeric order of discovery during the half-month.

So, we can see that the first Comet LINEAR, P/1997 A2, is a periodic comet discovered in 1997, between January 1 and January 15 of that year, and it was the second comet to be discovered during that period of time. After the second perihelion passage, P/1997 A2 (LINEAR) was subsequently given the periodic comet number prefix of 230, so the full designation for this comet is now 230P/1997 A2 (LINEAR).

Likewise, the most recent Comet LINEAR (at the time of this writing), C/2017 B3, is a non-periodic comet discovered in 2017 between January 16 and January 31, the third comet discovered during that period of time.

Interestingly, if different periodic comets have the same name, they are sequentially numbered. Perhaps the most famous example is Comet Shoemaker-Levy 9 that broke up and crashed into Jupiter during July 1994. There are a total of nine periodic comets named Shoemaker-Levy. They are:

192P/1990 V1 Shoemaker-Levy 1

137P/1990 UL3 Shoemaker-Levy 2

129P/1991 C1 Shoemaker-Levy 3

118P/1991 C2 Shoemaker-Levy 4

145P/1991 T1 Shoemaker-Levy 5

181P/1991 V1 Shoemaker-Levy 6

138P/1991 V2 Shoemaker-Levy 7

135P/1992 G2 Shoemaker-Levy 8

D/1993 F2 Shoemaker-Levy 9

However, four additional non-periodic comets were discovered by the Carolyn & Gene Shoemaker and David Levy team. They have not received a numeric suffix and are all called “Comet Shoemaker-Levy”:

C/1991 B1 Shoemaker-Levy

C/1991 T2 Shoemaker-Levy

C/1993 K1 Shoemaker-Levy

C/1994 E2 Shoemaker-Levy

This strikes me as a bit strange. Why afford a numeric suffix to a comet name only when it is a periodic comet? Why not give all comets named “Shoemaker-Levy” a numeric suffix. Normally, we would number them all in order of discovery, but since the nine periodic comets have already received a number, we would have to number the four non-periodic comets as C/1991 B1 (Shoemaker-Levy 10), C/1991 T2 (Shoemaker-Levy 11), C/1993 K1 (Shoemaker-Levy 12), and C/1994 E2 (Shoemaker-Levy 13).

I would like to see all comets, both periodic and non-periodic, receive a numeric suffix to their names whenever there is more than one. So, instead of Comet LINEAR we would have Comet LINEAR 1, Comet LINEAR 2, Comet LINEAR 3, and so on.

By the way, the days of amateur astronomers discovering a new comet will probably soon come to a close. Though this is a little sad, it does tell us that the entire sky is being monitored much more closely than in the past, by a number of automated surveys. And that is a good thing, because we will be much less likely to miss anything “new” in the sky.

NoneOne of the comets this year (so far) havehas been discovered by amateurs.

UPDATE – November 20, 2018: California amateur astronomer and prolific comet hunter Don Machholz, along with Japanese amateur astronomers Shigehisa Fujikawa and Masayuki Iwamoto, independently discovered a new comet on November 7. The new long-period comet has been named C/2018 V1 (Machholz-Fujikawa-Iwamoto). Remarkable!

Here is the current tally of comet discoveries (or recoveries) this year:

Mark Whittle, Professor of Astronomy at the University of Virginia, has put together the most comprehensive and comprehensible treatment on the subject of cosmology that I have ever encountered. Cosmology: The History and Nature of Our Universe, a series of 36 thirty-minute video lectures for The Great Courses (Course No. 1830), is a truly remarkable achievement.

Even though this course was released ten years ago in 2008, all of the material is still completely relevant. This is the course on cosmology that I’ve always wanted but never had. Enjoy!

Cosmology has come a long ways since I was a physics and astronomy student at Iowa State University from 1975-1980, and again in 1981, 1984, and 2000-2005. I’m glad to see a course specifically about cosmology is now offered at a number of universities. When I was an undergraduate student at ISU, it was unheard of. The University of Wisconsin at Madison Department of Astronomy currently offers both an undergraduate and a graduate course in cosmology: Astronomy 335 – Cosmology, and Astronomy 735 – Observational Cosmology. And the Department of Physics & Astronomy at Iowa State University now offers an undergraduate/graduate dual-listed cosmology course: Astro 405/505 – Astrophysical Cosmology.

When I retire in a few years, I would love to be a “fly on the wall” at the UW-Madison astronomy department. Wonder if they could use an expert SAS programmer to help analyze the massive quantities of data they surely must have? (Though the last time I interviewed for an astronomy job, at the McDonald Observatory in Texas, the interviewers had never heard of SAS but asked if I knew Python, which of course is what nearly everyone is looking for and using these days. Tomorrow, it will be something else…). In retirement, at the very least I would love to immerse myself in a few astronomy courses at UW-Madison. Something to look forward to!

One by one, all of our warm white lights are being replaced by cold, harsh, bluish-white LEDs. And it is happening fast.

Everywhere. In our streetlights, our workplaces, even our homes. How do you like looking into those blue-white vehicle headlights as compared with the yellow-white ones we have been using since the automobile was invented?

LED lighting is the way of the future, don’t get me wrong, but we should be specifying and installing LED lights with a correlated color temperature (CCT) of 2700K or 3000K—with few exceptions—not the 4000K or higher that is the current standard.

Why is 4000K the current standard? Because blue-white LEDs have a slightly greater luminous efficacy than yellow-white LEDs. Luminous efficacy is the amount of light you get out for the power you put in, often measured in lumens per watt. But should luminous efficiency be the only consideration? What about aesthetics? In addition to luminous efficacy, there are other, more significant ways to reduce power consumption and greenhouse gas emissions:

Use the minimum amount of light needed for the application; no need to overlight

Use efficient light fixtures that direct light only to where it is needed; near-horizontal light creates annoying and visibility-impairing glare and light trespass, and direct uplight into the night sky is a complete waste

Produce the light only when it is needed through simple switches, time controls, and occupancy sensors; or, use lower light levels during times of little or no activity

Even the super-inefficient incandescent light bulb (with a CCT of 2400K, by the way), operating three hours each night uses less energy than the light source with the highest luminous efficacy operating dusk to dawn. Think about it.

In my town, as in most now, the soothing orange 1900K high pressure sodium (HPS) streetlights are being replaced with 4000K LEDs. That’s a big change. It will completely transform our outdoor nighttime environment. Warm-white compact fluorescents are 2700K, and even tungsten halogen bulbs are 3000K. Do we really want or need 4000K+ LEDs?

We are currently witnessing a complete transformation of our illuminated built environment. Not enough questions are being asked nor direction being given by citizens, employees, and municipalities. The lighting industry generally wants to sell as many lights as possible at the highest profit margin. We as lighting consumers need to make sure we have the right kind of light, the right amount of light, and lighting only when and where it is needed.

Higher color-temperature lighting of 3500K or higher is often specified for office lighting during the day to more closely match daylight color temperature, but all to often this type of lighting is also being specified for nighttime use. Lower color temperature lighting of 2700K or 3000K should be used for residential lighting and any other lighting that is primarily being used after sunset, such as streetlighting, parking lot lighting, and security lighting.